An elevator typically comprises a hoisting roping suspending a vertically movable elevator car. The elevator further comprises a drive machine which drives the elevator car under control of an elevator control system. The driving force is typically transmitted from the drive machine to the car via said hoisting roping. The drive machine typically comprises a motor and a drive wheel engaging the individual ropes of the hoisting roping each of the ropes passing around the drive wheel and being connected to the car. The material and overall structure of the rope affects several properties of the rope, which are important for the elevator. In particular, the minimal bending radius of the rope, the weight of the rope, the force transmission ability of the rope as such, as well as the force transmission ability via the engagement between the rope and the drive wheel are all affected by the material and overall structure of the rope. These properties affect the properties of the complete elevator. In particular, the minimal bending radius of the rope is important as it sets a lower limit for the radius of the wheels around which the rope passes in the elevator.
A large bending radius may reduce the space efficiency of the elevator as well as make the layout of the elevator more complicated. The drive wheel may also be necessary to be designed with a radius larger than optimal in terms of torque production and rotational speed. Heavy weight of each rope and the overall weight of the roping reduces energy efficiency of the elevator. The force transmission ability of each rope should therefore be as great as possible relative to the weight of the rope. These properties have been optimized in the rope as disclosed in international patent application WO2009090299 A1 for instance. In this particular case, a wide surface is provided for the rope which facilitates firm engagement with a drive wheel. The surface material is elastomeric, which provides protection for the rope inner parts and/or high friction thereby facilitating firm engagement with a drive wheel.
A problem with the solutions according to prior art is that it is difficult to form a rope which has a high load bearing ability (in particular tensile strength) relative to weight of the rope while at the same time making the rope bendable with a reasonably small bending radius and yet having a surface enabling good protection for the inner parts and/or good force transmitting abilities via the surface.